Either way, I have three issues I hope to get solved.The first one is pretty obvious and can be seen in the in-game screenshot. There is a blurry weird looking reflection of the light/lamp prop. I don't know exactly what causes it (although it is clearly related to the cubemaps). I tried increasing the number of cubemaps, decreasing the number of cubemaps, changing which faces the cubemaps are assigned to and so on but so far I haven't gotten rid of this weird reflection. Actually the only way I found to get rid of this issue is to change from prop_static to prop_dynamic_override, in which case it looks like this:

In this case there are no reflections at all, not even in the scope of the moonraker. It gets rid of the problem but it looks dry.

A somewhat related issue is that I want to be able to decrease the intensity of lamp/light texture. It shouldn't be as bright as it is. I've looked into it a bit but I'm still not sure how it's done.

The third issue is that when applying a material using cubemaps on certain brushes there are weird edges visible. This can be clearly seen in these images:

I solved the weird texture edge issue mostly by adjusting the lightmap scale and sometimes rotating the texture (which works for some reason). I "solved" the weird reflection issue by setting the light/lamp props to prop_dynamic_override so that they aren't included in the cubemap reflection. Maybe I will change it later but for now this is the simplest and best solution (getting the proper reflections (if possible) seems like a lot of work).

Edit: The remaining issue is whether or not I can adjust the intensity of the self-illuminating texture on the light/lamp prop.